Technical Articles
Features of the Trunnion Mounted Ball Valve
Posted: 06/03/2017 14:14:35  Hits: 7
The balls of the trunnion mounted ball valve are fixed and will not move after the pressure. Therefore, the two seal rings should be designed to have sufficient pretightening force to ensure that the seal is a double-sided forced seal. Usually, the upper and lower valve stem which is connected to the ball is equipped with thrust or sliding bearings.
1. Reliable sealing performance: The PTFE sealing ring is embedded in the stainless steel valve seat and there is the spring at the end of the metal valve seat to ensure that the seal ring has enough pretightening force. If the sealing surface of the trunnion mounted ball valve is wearing out in the use, the valve can keep its good sealing performance under the effects of the spring.
2. Effort saving operation: The ball is supported by the upper and lower bearing and  the friction is reduced. It eliminates the too large torque pressure caused by the huge sealing load, formed by the inlet pressure pushing the ball and the sealing seat.
3. Fireproof structure: In order to prevent the emergence of sudden heat or fire, which will burn the Teflon seal ring and cause a great leakage, finally to contribute to the fire, there is a fireproof seal ring between the ball and the valve seat. If the seal ring is burnt, under the effects of the spring force, the seal ring of the valve seat will be quickly pushed to the ball and the seal between metal and metal will be formed to obtain the sealing effect. The refractory test meets APl6FA and APl607 standards.
4. Automatic pressure relief function: When the medium pressure in the middle valve cavity becomes abnormal or rises exceeding the pretightening force of the spring, the valve seat will back from the ball, to achieve the effect of automatic pressure relief, and the valve seat will back to the original position automatically after relief.  
5. The discharge pipeline: The upper and lower valve bodies are equipped with discharge holes, which can check whether there is a leakage occurring in the valve seat. When the valve is completely opened or closed, we can directly replace the packing after relieving the pressure in the valve cavity. The discharge pipelines can let the media in the middle cavity out, thus can reduce the valve pollution.
The trunnion mounted ball valve can be applied for pipelines with pressure from Class150 to Class1500, from PN16 to PN100, or from JIS10K to JIS20K and with applicable temperature from -196℃ to 350℃. They can be used to cut off or connect the media in the pipe. Being made from different materials, they can be widely used in the petroleum refining, long-distance pipeline, chemical industry, paper making, pharmaceutical, water conservancy, electric power, steel, etc. The drive modes of the trunnion mounted ball valve include worm gear operated, manual, pneumatic and electric drive modes. Trunnion mounted ball valves generally adopt the flanged connection and sometimes adopt the welded connection.